Predictive importance of cartilage acetabular index for acetabular dysplasia

Aim: The goal in the treatment of developmental dysplasia of the hip is to achieve a stable hip joint by providing concentric reduction and to achieve normal acetabular development. One of the most important factors affecting normal acetabular development is the acetabular cover. The relation of the acetabular development with the bone acetabular index, a widely used method to evaluate acetabular coverage, is now being questioned. However, studies which is the importance of cartilaginous acetabular index that show cartilaginous acetabular cover are limited and the importance is not well known. In the present study, we investigated the relationship between cartilage acetabular index which showed cartilaginous cover, acetabular development and secondary dysplasia. Material and Method: A total of 39 patients, 35 female and 4 male, including 58 hips who underwent open reduction or limited open reduction by intraoperative arthrography due to developmental dysplasia of the hip between 2011 and 2015 were included in the study at Department of Orthopedics and Traumatology, Dicle University Faculty of Medicine. Intraoperative acetabular cartilage index measurements were performed and patients were divided into two groups according to low and high cartilage acetabular index. Group 1, consist of a cartilaginous acetabular index below 80 and group 2, consist of a cartilaginous acetabular index 80 and above was determined. To determine the importance of cartilage acetabular index, patients with at least 24 months follow-up were compared regarding both osseous acetabular development and development of secondary dysplasia. A broken Shenton-Menard line, and an acetabular index (Ai) of 32° or higher two years after reduction were considered to be indicative of secondary acetabular dysplasia. Evidence: The youngest patient was six months old, the oldest was 30 months old, the average age was 14,34 months. The follow-up period of at least 24 months, a maximum of 40 months with a mean follow-up of 28.23 months. The intraoperative cartilage acetabular angle of the patients was evaluated according to bone acetabular index at postoperative 24th-month radiograph was interpreted for secondary acetabular dysplasia. 2 of 25 patients in group 1 and 14 of 33 patients in group 2 were found 32° and above. The intraoperative cartilage acetabular angle of the patients was evaluated according to a broken Shenton-Menard line is interpreted for secondary acetabular dysplasia. 1 of 25 patients in group 1 and 9 of 33 patients in group 2 were found 32° and above. Patients' intraoperative cartilage acetabular angles showed a statistically significant change with respect to the bone acetabular index at the postoperative 24th-month radiograph and Shenton-Menard fracture for secondary acetabular dysplasia (p=0.006, p=0.033). One of 39 hips had Grade I avascular necrosis. Complications such as redislocation, subluxation, infection and femur fracture were not seen. Result: One of the most important factors affecting normal acetabular development in the treatment of developmental dysplasia of the hip is acetabular coverage. Measurement of cartilaginous acetabular index is a new method of evaluation. There is a correlation between cartilaginous acetabular index that shows preoperative cartilaginous acetabular coverage and acetabular development and secondary acetabular development according to our findings. In this study, it was concluded that cartilaginous acetabular index can be used to predict acetabular development. It is technically simple and uncomplicated. This method can be routinely used for acetabular index evaluation along with the bone acetabular index.